status.c

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/*
 * Copyright 2002-2005, Instant802 Networks, Inc.
 * Copyright 2005-2006, Devicescape Software, Inc.
 * Copyright 2006-2007  Jiri Benc <[email protected]>
 * Copyright 2008-2010  Johannes Berg <[email protected]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/export.h>
#include <linux/etherdevice.h>
#include <net/mac80211.h>
#include <asm/unaligned.h>
#include "ieee80211_i.h"
#include "rate.h"
#include "mesh.h"
#include "led.h"
#include "wme.h"


void ieee80211_tx_status_irqsafe(struct ieee80211_hw *hw,
                 struct sk_buff *skb)
{
    struct ieee80211_local *local = hw_to_local(hw);
    struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
    int tmp;

    skb->pkt_type = IEEE80211_TX_STATUS_MSG;
    skb_queue_tail(info->flags & IEEE80211_TX_CTL_REQ_TX_STATUS ?
               &local->skb_queue : &local->skb_queue_unreliable, skb);
    tmp = skb_queue_len(&local->skb_queue) +
        skb_queue_len(&local->skb_queue_unreliable);
    while (tmp > IEEE80211_IRQSAFE_QUEUE_LIMIT &&
           (skb = skb_dequeue(&local->skb_queue_unreliable))) {
        ieee80211_free_txskb(hw, skb);
        tmp--;
        I802_DEBUG_INC(local->tx_status_drop);
    }
    tasklet_schedule(&local->tasklet);
}
EXPORT_SYMBOL(ieee80211_tx_status_irqsafe);

static void ieee80211_handle_filtered_frame(struct ieee80211_local *local,
                        struct sta_info *sta,
                        struct sk_buff *skb)
{
    struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
    struct ieee80211_hdr *hdr = (void *)skb->data;
    int ac;

    /*
     * This skb 'survived' a round-trip through the driver, and
     * hopefully the driver didn't mangle it too badly. However,
     * we can definitely not rely on the control information
     * being correct. Clear it so we don't get junk there, and
     * indicate that it needs new processing, but must not be
     * modified/encrypted again.
     */
    memset(&info->control, 0, sizeof(info->control));

    info->control.jiffies = jiffies;
    info->control.vif = &sta->sdata->vif;
    info->flags |= IEEE80211_TX_INTFL_NEED_TXPROCESSING |
               IEEE80211_TX_INTFL_RETRANSMISSION;
    info->flags &= ~IEEE80211_TX_TEMPORARY_FLAGS;

    sta->tx_filtered_count++;

    /*
     * Clear more-data bit on filtered frames, it might be set
     * but later frames might time out so it might have to be
     * clear again ... It's all rather unlikely (this frame
     * should time out first, right?) but let's not confuse
     * peers unnecessarily.
     */
    if (hdr->frame_control & cpu_to_le16(IEEE80211_FCTL_MOREDATA))
        hdr->frame_control &= ~cpu_to_le16(IEEE80211_FCTL_MOREDATA);

    if (ieee80211_is_data_qos(hdr->frame_control)) {
        u8 *p = ieee80211_get_qos_ctl(hdr);
        int tid = *p & IEEE80211_QOS_CTL_TID_MASK;

        /*
         * Clear EOSP if set, this could happen e.g.
         * if an absence period (us being a P2P GO)
         * shortens the SP.
         */
        if (*p & IEEE80211_QOS_CTL_EOSP)
            *p &= ~IEEE80211_QOS_CTL_EOSP;
        ac = ieee802_1d_to_ac[tid & 7];
    } else {
        ac = IEEE80211_AC_BE;
    }

    /*
     * Clear the TX filter mask for this STA when sending the next
     * packet. If the STA went to power save mode, this will happen
     * when it wakes up for the next time.
     */
    set_sta_flag(sta, WLAN_STA_CLEAR_PS_FILT);

    /*
     * This code races in the following way:
     *
     *  (1) STA sends frame indicating it will go to sleep and does so
     *  (2) hardware/firmware adds STA to filter list, passes frame up
     *  (3) hardware/firmware processes TX fifo and suppresses a frame
     *  (4) we get TX status before having processed the frame and
     *  knowing that the STA has gone to sleep.
     *
     * This is actually quite unlikely even when both those events are
     * processed from interrupts coming in quickly after one another or
     * even at the same time because we queue both TX status events and
     * RX frames to be processed by a tasklet and process them in the
     * same order that they were received or TX status last. Hence, there
     * is no race as long as the frame RX is processed before the next TX
     * status, which drivers can ensure, see below.
     *
     * Note that this can only happen if the hardware or firmware can
     * actually add STAs to the filter list, if this is done by the
     * driver in response to set_tim() (which will only reduce the race
     * this whole filtering tries to solve, not completely solve it)
     * this situation cannot happen.
     *
     * To completely solve this race drivers need to make sure that they
     *  (a) don't mix the irq-safe/not irq-safe TX status/RX processing
     *  functions and
     *  (b) always process RX events before TX status events if ordering
     *      can be unknown, for example with different interrupt status
     *  bits.
     *  (c) if PS mode transitions are manual (i.e. the flag
     *      %IEEE80211_HW_AP_LINK_PS is set), always process PS state
     *      changes before calling TX status events if ordering can be
     *  unknown.
     */
    if (test_sta_flag(sta, WLAN_STA_PS_STA) &&
        skb_queue_len(&sta->tx_filtered[ac]) < STA_MAX_TX_BUFFER) {
        skb_queue_tail(&sta->tx_filtered[ac], skb);
        sta_info_recalc_tim(sta);

        if (!timer_pending(&local->sta_cleanup))
            mod_timer(&local->sta_cleanup,
                  round_jiffies(jiffies +
                        STA_INFO_CLEANUP_INTERVAL));
        return;
    }

    if (!test_sta_flag(sta, WLAN_STA_PS_STA) &&
        !(info->flags & IEEE80211_TX_INTFL_RETRIED)) {
        /* Software retry the packet once */
        info->flags |= IEEE80211_TX_INTFL_RETRIED;
        ieee80211_add_pending_skb(local, skb);
        return;
    }

    ps_dbg_ratelimited(sta->sdata,
               "dropped TX filtered frame, queue_len=%d PS=%d @%lu\n",
               skb_queue_len(&sta->tx_filtered[ac]),
               !!test_sta_flag(sta, WLAN_STA_PS_STA), jiffies);
    ieee80211_free_txskb(&local->hw, skb);
}

static void ieee80211_check_pending_bar(struct sta_info *sta, u8 *addr, u8 tid)
{
    struct tid_ampdu_tx *tid_tx;

    tid_tx = rcu_dereference(sta->ampdu_mlme.tid_tx[tid]);
    if (!tid_tx || !tid_tx->bar_pending)
        return;

    tid_tx->bar_pending = false;
    ieee80211_send_bar(&sta->sdata->vif, addr, tid, tid_tx->failed_bar_ssn);
}

static void ieee80211_frame_acked(struct sta_info *sta, struct sk_buff *skb)
{
    struct ieee80211_mgmt *mgmt = (void *) skb->data;
    struct ieee80211_local *local = sta->local;
    struct ieee80211_sub_if_data *sdata = sta->sdata;

    if (ieee80211_is_data_qos(mgmt->frame_control)) {
        struct ieee80211_hdr *hdr = (void *) skb->data;
        u8 *qc = ieee80211_get_qos_ctl(hdr);
        u16 tid = qc[0] & 0xf;

        ieee80211_check_pending_bar(sta, hdr->addr1, tid);
    }

    if (ieee80211_is_action(mgmt->frame_control) &&
        sdata->vif.type == NL80211_IFTYPE_STATION &&
        mgmt->u.action.category == WLAN_CATEGORY_HT &&
        mgmt->u.action.u.ht_smps.action == WLAN_HT_ACTION_SMPS) {
        /*
         * This update looks racy, but isn't -- if we come
         * here we've definitely got a station that we're
         * talking to, and on a managed interface that can
         * only be the AP. And the only other place updating
         * this variable is before we're associated.
         */
        switch (mgmt->u.action.u.ht_smps.smps_control) {
        case WLAN_HT_SMPS_CONTROL_DYNAMIC:
            sta->sdata->u.mgd.ap_smps = IEEE80211_SMPS_DYNAMIC;
            break;
        case WLAN_HT_SMPS_CONTROL_STATIC:
            sta->sdata->u.mgd.ap_smps = IEEE80211_SMPS_STATIC;
            break;
        case WLAN_HT_SMPS_CONTROL_DISABLED:
        default: /* shouldn't happen since we don't send that */
            sta->sdata->u.mgd.ap_smps = IEEE80211_SMPS_OFF;
            break;
        }

        ieee80211_queue_work(&local->hw, &local->recalc_smps);
    }
}

static void ieee80211_set_bar_pending(struct sta_info *sta, u8 tid, u16 ssn)
{
    struct tid_ampdu_tx *tid_tx;

    tid_tx = rcu_dereference(sta->ampdu_mlme.tid_tx[tid]);
    if (!tid_tx)
        return;

    tid_tx->failed_bar_ssn = ssn;
    tid_tx->bar_pending = true;
}

static int ieee80211_tx_radiotap_len(struct ieee80211_tx_info *info)
{
    int len = sizeof(struct ieee80211_radiotap_header);

    /* IEEE80211_RADIOTAP_RATE rate */
    if (info->status.rates[0].idx >= 0 &&
        !(info->status.rates[0].flags & IEEE80211_TX_RC_MCS))
        len += 2;

    /* IEEE80211_RADIOTAP_TX_FLAGS */
    len += 2;

    /* IEEE80211_RADIOTAP_DATA_RETRIES */
    len += 1;

    /* IEEE80211_TX_RC_MCS */
    if (info->status.rates[0].idx >= 0 &&
        info->status.rates[0].flags & IEEE80211_TX_RC_MCS)
        len += 3;

    return len;
}

static void ieee80211_add_tx_radiotap_header(struct ieee80211_supported_band
                         *sband, struct sk_buff *skb,
                         int retry_count, int rtap_len)
{
    struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
    struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
    struct ieee80211_radiotap_header *rthdr;
    unsigned char *pos;
    u16 txflags;

    rthdr = (struct ieee80211_radiotap_header *) skb_push(skb, rtap_len);

    memset(rthdr, 0, rtap_len);
    rthdr->it_len = cpu_to_le16(rtap_len);
    rthdr->it_present =
        cpu_to_le32((1 << IEEE80211_RADIOTAP_TX_FLAGS) |
                (1 << IEEE80211_RADIOTAP_DATA_RETRIES));
    pos = (unsigned char *)(rthdr + 1);

    /*
     * XXX: Once radiotap gets the bitmap reset thing the vendor
     *  extensions proposal contains, we can actually report
     *  the whole set of tries we did.
     */

    /* IEEE80211_RADIOTAP_RATE */
    if (info->status.rates[0].idx >= 0 &&
        !(info->status.rates[0].flags & IEEE80211_TX_RC_MCS)) {
        rthdr->it_present |= cpu_to_le32(1 << IEEE80211_RADIOTAP_RATE);
        *pos = sband->bitrates[info->status.rates[0].idx].bitrate / 5;
        /* padding for tx flags */
        pos += 2;
    }

    /* IEEE80211_RADIOTAP_TX_FLAGS */
    txflags = 0;
    if (!(info->flags & IEEE80211_TX_STAT_ACK) &&
        !is_multicast_ether_addr(hdr->addr1))
        txflags |= IEEE80211_RADIOTAP_F_TX_FAIL;

    if ((info->status.rates[0].flags & IEEE80211_TX_RC_USE_RTS_CTS) ||
        (info->status.rates[0].flags & IEEE80211_TX_RC_USE_CTS_PROTECT))
        txflags |= IEEE80211_RADIOTAP_F_TX_CTS;
    else if (info->status.rates[0].flags & IEEE80211_TX_RC_USE_RTS_CTS)
        txflags |= IEEE80211_RADIOTAP_F_TX_RTS;

    put_unaligned_le16(txflags, pos);
    pos += 2;

    /* IEEE80211_RADIOTAP_DATA_RETRIES */
    /* for now report the total retry_count */
    *pos = retry_count;
    pos++;

    /* IEEE80211_TX_RC_MCS */
    if (info->status.rates[0].idx >= 0 &&
        info->status.rates[0].flags & IEEE80211_TX_RC_MCS) {
        rthdr->it_present |= cpu_to_le32(1 << IEEE80211_RADIOTAP_MCS);
        pos[0] = IEEE80211_RADIOTAP_MCS_HAVE_MCS |
             IEEE80211_RADIOTAP_MCS_HAVE_GI |
             IEEE80211_RADIOTAP_MCS_HAVE_BW;
        if (info->status.rates[0].flags & IEEE80211_TX_RC_SHORT_GI)
            pos[1] |= IEEE80211_RADIOTAP_MCS_SGI;
        if (info->status.rates[0].flags & IEEE80211_TX_RC_40_MHZ_WIDTH)
            pos[1] |= IEEE80211_RADIOTAP_MCS_BW_40;
        if (info->status.rates[0].flags & IEEE80211_TX_RC_GREEN_FIELD)
            pos[1] |= IEEE80211_RADIOTAP_MCS_FMT_GF;
        pos[2] = info->status.rates[0].idx;
        pos += 3;
    }

}

/*
 * Use a static threshold for now, best value to be determined
 * by testing ...
 * Should it depend on:
 *  - on # of retransmissions
 *  - current throughput (higher value for higher tpt)?
 */
#define STA_LOST_PKT_THRESHOLD  50

void ieee80211_tx_status(struct ieee80211_hw *hw, struct sk_buff *skb)
{
    struct sk_buff *skb2;
    struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
    struct ieee80211_local *local = hw_to_local(hw);
    struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
    __le16 fc;
    struct ieee80211_supported_band *sband;
    struct ieee80211_sub_if_data *sdata;
    struct net_device *prev_dev = NULL;
    struct sta_info *sta, *tmp;
    int retry_count = -1, i;
    int rates_idx = -1;
    bool send_to_cooked;
    bool acked;
    struct ieee80211_bar *bar;
    int rtap_len;

    for (i = 0; i < IEEE80211_TX_MAX_RATES; i++) {
        if ((info->flags & IEEE80211_TX_CTL_AMPDU) &&
            !(info->flags & IEEE80211_TX_STAT_AMPDU)) {
            /* just the first aggr frame carry status info */
            info->status.rates[i].idx = -1;
            info->status.rates[i].count = 0;
            break;
        } else if (info->status.rates[i].idx < 0) {
            break;
        } else if (i >= hw->max_report_rates) {
            /* the HW cannot have attempted that rate */
            info->status.rates[i].idx = -1;
            info->status.rates[i].count = 0;
            break;
        }

        retry_count += info->status.rates[i].count;
    }
    rates_idx = i - 1;

    if (retry_count < 0)
        retry_count = 0;

    rcu_read_lock();

    sband = local->hw.wiphy->bands[info->band];
    fc = hdr->frame_control;

    for_each_sta_info(local, hdr->addr1, sta, tmp) {
        /* skip wrong virtual interface */
        if (!ether_addr_equal(hdr->addr2, sta->sdata->vif.addr))
            continue;

        if (info->flags & IEEE80211_TX_STATUS_EOSP)
            clear_sta_flag(sta, WLAN_STA_SP);

        acked = !!(info->flags & IEEE80211_TX_STAT_ACK);
        if (!acked && test_sta_flag(sta, WLAN_STA_PS_STA)) {
            /*
             * The STA is in power save mode, so assume
             * that this TX packet failed because of that.
             */
            ieee80211_handle_filtered_frame(local, sta, skb);
            rcu_read_unlock();
            return;
        }

        if ((local->hw.flags & IEEE80211_HW_HAS_RATE_CONTROL) &&
            (rates_idx != -1))
            sta->last_tx_rate = info->status.rates[rates_idx];

        if ((info->flags & IEEE80211_TX_STAT_AMPDU_NO_BACK) &&
            (ieee80211_is_data_qos(fc))) {
            u16 tid, ssn;
            u8 *qc;

            qc = ieee80211_get_qos_ctl(hdr);
            tid = qc[0] & 0xf;
            ssn = ((le16_to_cpu(hdr->seq_ctrl) + 0x10)
                        & IEEE80211_SCTL_SEQ);
            ieee80211_send_bar(&sta->sdata->vif, hdr->addr1,
                       tid, ssn);
        }

        if (!acked && ieee80211_is_back_req(fc)) {
            u16 tid, control;

            /*
             * BAR failed, store the last SSN and retry sending
             * the BAR when the next unicast transmission on the
             * same TID succeeds.
             */
            bar = (struct ieee80211_bar *) skb->data;
            control = le16_to_cpu(bar->control);
            if (!(control & IEEE80211_BAR_CTRL_MULTI_TID)) {
                u16 ssn = le16_to_cpu(bar->start_seq_num);

                tid = (control &
                       IEEE80211_BAR_CTRL_TID_INFO_MASK) >>
                      IEEE80211_BAR_CTRL_TID_INFO_SHIFT;

                ieee80211_set_bar_pending(sta, tid, ssn);
            }
        }

        if (info->flags & IEEE80211_TX_STAT_TX_FILTERED) {
            ieee80211_handle_filtered_frame(local, sta, skb);
            rcu_read_unlock();
            return;
        } else {
            if (!acked)
                sta->tx_retry_failed++;
            sta->tx_retry_count += retry_count;
        }

        rate_control_tx_status(local, sband, sta, skb);
        if (ieee80211_vif_is_mesh(&sta->sdata->vif))
            ieee80211s_update_metric(local, sta, skb);

        if (!(info->flags & IEEE80211_TX_CTL_INJECTED) && acked)
            ieee80211_frame_acked(sta, skb);

        if ((sta->sdata->vif.type == NL80211_IFTYPE_STATION) &&
            (local->hw.flags & IEEE80211_HW_REPORTS_TX_ACK_STATUS))
            ieee80211_sta_tx_notify(sta->sdata, (void *) skb->data, acked);

        if (local->hw.flags & IEEE80211_HW_REPORTS_TX_ACK_STATUS) {
            if (info->flags & IEEE80211_TX_STAT_ACK) {
                if (sta->lost_packets)
                    sta->lost_packets = 0;
            } else if (++sta->lost_packets >= STA_LOST_PKT_THRESHOLD) {
                cfg80211_cqm_pktloss_notify(sta->sdata->dev,
                                sta->sta.addr,
                                sta->lost_packets,
                                GFP_ATOMIC);
                sta->lost_packets = 0;
            }
        }
    }

    rcu_read_unlock();

    ieee80211_led_tx(local, 0);

    /* SNMP counters
     * Fragments are passed to low-level drivers as separate skbs, so these
     * are actually fragments, not frames. Update frame counters only for
     * the first fragment of the frame. */
    if (info->flags & IEEE80211_TX_STAT_ACK) {
        if (ieee80211_is_first_frag(hdr->seq_ctrl)) {
            local->dot11TransmittedFrameCount++;
            if (is_multicast_ether_addr(hdr->addr1))
                local->dot11MulticastTransmittedFrameCount++;
            if (retry_count > 0)
                local->dot11RetryCount++;
            if (retry_count > 1)
                local->dot11MultipleRetryCount++;
        }

        /* This counter shall be incremented for an acknowledged MPDU
         * with an individual address in the address 1 field or an MPDU
         * with a multicast address in the address 1 field of type Data
         * or Management. */
        if (!is_multicast_ether_addr(hdr->addr1) ||
            ieee80211_is_data(fc) ||
            ieee80211_is_mgmt(fc))
            local->dot11TransmittedFragmentCount++;
    } else {
        if (ieee80211_is_first_frag(hdr->seq_ctrl))
            local->dot11FailedCount++;
    }

    if (ieee80211_is_nullfunc(fc) && ieee80211_has_pm(fc) &&
        (local->hw.flags & IEEE80211_HW_REPORTS_TX_ACK_STATUS) &&
        !(info->flags & IEEE80211_TX_CTL_INJECTED) &&
        local->ps_sdata && !(local->scanning)) {
        if (info->flags & IEEE80211_TX_STAT_ACK) {
            local->ps_sdata->u.mgd.flags |=
                    IEEE80211_STA_NULLFUNC_ACKED;
        } else
            mod_timer(&local->dynamic_ps_timer, jiffies +
                    msecs_to_jiffies(10));
    }

    if (info->flags & IEEE80211_TX_INTFL_NL80211_FRAME_TX) {
        u64 cookie = (unsigned long)skb;
        bool found = false;

        acked = info->flags & IEEE80211_TX_STAT_ACK;

        rcu_read_lock();

        list_for_each_entry_rcu(sdata, &local->interfaces, list) {
            if (!sdata->dev)
                continue;

            if (skb->dev != sdata->dev)
                continue;

            found = true;
            break;
        }

        if (!skb->dev) {
            sdata = rcu_dereference(local->p2p_sdata);
            if (sdata)
                found = true;
        }

        if (!found)
            skb->dev = NULL;
        else if (ieee80211_is_nullfunc(hdr->frame_control) ||
             ieee80211_is_qos_nullfunc(hdr->frame_control)) {
            cfg80211_probe_status(sdata->dev, hdr->addr1,
                          cookie, acked, GFP_ATOMIC);
        } else {
            cfg80211_mgmt_tx_status(&sdata->wdev, cookie, skb->data,
                        skb->len, acked, GFP_ATOMIC);
        }

        rcu_read_unlock();
    }

    if (unlikely(info->ack_frame_id)) {
        struct sk_buff *ack_skb;
        unsigned long flags;

        spin_lock_irqsave(&local->ack_status_lock, flags);
        ack_skb = idr_find(&local->ack_status_frames,
                   info->ack_frame_id);
        if (ack_skb)
            idr_remove(&local->ack_status_frames,
                   info->ack_frame_id);
        spin_unlock_irqrestore(&local->ack_status_lock, flags);

        /* consumes ack_skb */
        if (ack_skb)
            skb_complete_wifi_ack(ack_skb,
                info->flags & IEEE80211_TX_STAT_ACK);
    }

    /* this was a transmitted frame, but now we want to reuse it */
    skb_orphan(skb);

    /* Need to make a copy before skb->cb gets cleared */
    send_to_cooked = !!(info->flags & IEEE80211_TX_CTL_INJECTED) ||
             !(ieee80211_is_data(fc));

    /*
     * This is a bit racy but we can avoid a lot of work
     * with this test...
     */
    if (!local->monitors && (!send_to_cooked || !local->cooked_mntrs)) {
        dev_kfree_skb(skb);
        return;
    }

    /* send frame to monitor interfaces now */
    rtap_len = ieee80211_tx_radiotap_len(info);
    if (WARN_ON_ONCE(skb_headroom(skb) < rtap_len)) {
        pr_err("ieee80211_tx_status: headroom too small\n");
        dev_kfree_skb(skb);
        return;
    }
    ieee80211_add_tx_radiotap_header(sband, skb, retry_count, rtap_len);

    /* XXX: is this sufficient for BPF? */
    skb_set_mac_header(skb, 0);
    skb->ip_summed = CHECKSUM_UNNECESSARY;
    skb->pkt_type = PACKET_OTHERHOST;
    skb->protocol = htons(ETH_P_802_2);
    memset(skb->cb, 0, sizeof(skb->cb));

    rcu_read_lock();
    list_for_each_entry_rcu(sdata, &local->interfaces, list) {
        if (sdata->vif.type == NL80211_IFTYPE_MONITOR) {
            if (!ieee80211_sdata_running(sdata))
                continue;

            if ((sdata->u.mntr_flags & MONITOR_FLAG_COOK_FRAMES) &&
                !send_to_cooked)
                continue;

            if (prev_dev) {
                skb2 = skb_clone(skb, GFP_ATOMIC);
                if (skb2) {
                    skb2->dev = prev_dev;
                    netif_rx(skb2);
                }
            }

            prev_dev = sdata->dev;
        }
    }
    if (prev_dev) {
        skb->dev = prev_dev;
        netif_rx(skb);
        skb = NULL;
    }
    rcu_read_unlock();
    dev_kfree_skb(skb);
}
EXPORT_SYMBOL(ieee80211_tx_status);

void ieee80211_report_low_ack(struct ieee80211_sta *pubsta, u32 num_packets)
{
    struct sta_info *sta = container_of(pubsta, struct sta_info, sta);
    cfg80211_cqm_pktloss_notify(sta->sdata->dev, sta->sta.addr,
                    num_packets, GFP_ATOMIC);
}
EXPORT_SYMBOL(ieee80211_report_low_ack);

void ieee80211_free_txskb(struct ieee80211_hw *hw, struct sk_buff *skb)
{
    struct ieee80211_local *local = hw_to_local(hw);
    struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);

    if (unlikely(info->ack_frame_id)) {
        struct sk_buff *ack_skb;
        unsigned long flags;

        spin_lock_irqsave(&local->ack_status_lock, flags);
        ack_skb = idr_find(&local->ack_status_frames,
                   info->ack_frame_id);
        if (ack_skb)
            idr_remove(&local->ack_status_frames,
                   info->ack_frame_id);
        spin_unlock_irqrestore(&local->ack_status_lock, flags);

        /* consumes ack_skb */
        if (ack_skb)
            dev_kfree_skb_any(ack_skb);
    }

    dev_kfree_skb_any(skb);
}
EXPORT_SYMBOL(ieee80211_free_txskb);

void ieee80211_purge_tx_queue(struct ieee80211_hw *hw,
                  struct sk_buff_head *skbs)
{
    struct sk_buff *skb;

    while ((skb = __skb_dequeue(skbs)))
        ieee80211_free_txskb(hw, skb);
}